**Core Concept**
Purine metabolism is a complex process that involves the breakdown of purine nucleotides to produce a final end product. This process is crucial for maintaining homeostasis and preventing the accumulation of toxic purine metabolites.

**Why the Correct Answer is Right**
The end product of purine metabolism is uric acid, which is formed through the sequential breakdown of purine nucleotides. This process involves the action of the enzyme xanthine oxidase, which catalyzes the oxidation of hypoxanthine to xanthine and then to uric acid. Uric acid is then excreted in the urine.

**Why Each Wrong Option is Incorrect**
**Option A:** Urea is the end product of protein metabolism, not purine metabolism.
**Option B:** Creatinine is a byproduct of muscle metabolism, not purine metabolism.
**Option C:** Adenosine is a nucleoside involved in various physiological processes, but it is not the end product of purine metabolism.

**Clinical Pearl / High-Yield Fact**
It is essential to note that an excess of uric acid can lead to hyperuricemia, which is associated with conditions such as gout and kidney stones. Aspirin and certain diuretics can increase uric acid levels, making it crucial to monitor uric acid levels in patients taking these medications.

**Correct Answer: C. Uric acid**